Banding of articles with a plastics film material is a widely known procedure. Rolls of thin plastic film are commonly sold to householders, generally for use in the kitchen to wrap foods. Such films in various chemical compositions are also widely used in what is called the shrink film art. In that art, articles of many different sizes and shapes are encircled with a relatively loose band of plastic film and then heated to cause the film to melt from the crystalline state to the amorphous state and thereby shrink about the article. Subsequent cooling returns the film to the crystalline state. Articles so packaged often have the appearance of a stretched film band because of the close conformity of the film to the article, but such bands exert no compressive forces on the packaged article.
With the growth of the plastic film industry many stretched film applications have been developed. Such films are commonly elastomeric materials made by blowing processes from a polymer such as polyethylene. Other polymers and many different additives are available to make films with various desireable properties such as high elasticity, high recovery rates and excellent creep resistance. Commonly those films are blown with wall thicknesses of from 1 to 4 mils. With such films an object can be wrapped or banded by stretching the film in application or prior to application, and in the resulting package high compressive forces of the film on the object will be maintained for considerable periods of time. Generally, the higher the initial stretching forces, the higher will be the resulting compressive forces of the stretched film. However, if the elastic limit of the material is exceeded in the stretching operation, the material will lose its elasticity and no longer produce elastic compressive forces.
One substantial commercial use of stretch film is for the wrapping of pallet loads of boxes. Usually a 1 mil thick, 12 inch wide, roll of stretch film is highly stretched and wound spirally in layer after layer about a pallet load of boxes. A very tightly and resiliently maintained pallet load is achieved which can be shipped great distances by rail or truck. Other applications for stretch film are known in the prior art, but they generally appear to involve relatively low degrees of stretch. One such application is for the packaging of frozen turkeys. A bag or tube of a plastic material with a relatively low recovery rate is initially radially stretched with a plurality of extending arms. The turkey is then placed within the stretched tube and the arms are then quickly radially retracted and axially drawn from the tube before the plastic can recover. Another low stretch application, which is often used for labeling, involves the radial stretching of a plastic tube with fingers, plates or rods followed by the insertion of the object to be packaged or labeled. Then with some slight retraction of the stretching fingers against the object, jaws, pads or other devices are then pressed against the film and the underlying object with a force sufficiently great to permit the object with the film thereabout to be drawn from the stretching fingers. It has been found that the foregoing procedure is impractical when the bands are highly-stretched because more often than not the film is torn, distorted or destroyed in the attempted withdrawal of the stretching elements.
One suitable arrangement in various embodiments is known which can apply a highly-stretched, relatively-thin and broad plastic film band about the body portions of a plurality of bottles. In that arrangement a plurality of generally curved jaw plates are inserted in a film band and then rotated or otherwise moved to stretch the band. The bottles are then placed within the band and the jaws are moved circumferentially about the surface of the bottles until they enter into the open spaces between adjacent bottles and the inner surface of the band. The package of bottles can then be easily removed from the stretching jaws. The foregoing arrangement is obviously not suitable for banding or packaging boxes or like articles because of the lack of any open areas into which the stretching elements may be removed.